HIGH SENSITIVITY SOLID STATE MAGNETOMETER

• US 20100308813A1
• Filed: 12/03/2008
• Published: 12/09/2010
• Est. Priority Date: 12/03/2007
• Status: Active Grant

• Current Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Original Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Inventors: Walsworth, Ronald L., Lukin, Mikhail
• Granted Patent: US 8,947,080 B2
• Time in Patent Office: Days
• US Class Current: 324/244.1
• CPC Class Codes: G01N 24/10 by using electron paramagnetic resonance G01N24/12 takes precedence
• CPC Class Codes: G01R 33/032 using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
• CPC Class Codes: G01R 33/1284 Spin resolved measurements; Influencing spins during measurements, e.g. in spintronics devices G01R33/093 takes precedence; semiconductor devices using spin polarized carriers H01L29/66984
• CPC Class Codes: G01R 33/24 for measuring direction or magnitude of magnetic fields or magnetic flux
• CPC Class Codes: G01R 33/60 using electron paramagnetic resonance G01R33/24, G01R33/62 take precedence

Abstract

A magnetometer for sensing a magnetic field may include a solid state electronic spin system, and a detector. The solid state electronic spin system may contain one or more electronic spins that are disposed within a solid state lattice, for example NV centers in diamond. The electronic spins may be configured to receive optical excitation radiation and to align with the magnetic field in response thereto. The electronic spins may be further induced to precess about the magnetic field to be sensed, in response to an external control such as an RF field, the frequency of the spin precession being linearly related to the magnetic field by the Zeeman shift of the electronic spin energy levels. The detector may be configured to detect output optical radiation from the electronic spin, so as to determine the Zeeman shift and thus the magnetic field.

Claims

1. A magnetometer for sensing a magnetic field, comprising:

a solid state electronic spin system containing one or more electronic spins that are disposed within a solid state lattice, and that are substantially free of interaction with the solid state lattice;

wherein the electronic spins are configured to align with the magnetic field in response to optical excitation radiation applied thereto; and

wherein the electronic spins can be further manipulated by an external control so as to induce a precession of the electronic spins about the magnetic field to be sensed, the frequency of the precession being linearly related to the magnetic field by the Zeeman shift of the electronic spin energy levels; and

a detector configured to detect output optical radiation correlated with the electronic spins, after the electronic spins have been subject to the optical excitation radiation and the external control, so as to determine the Zeeman shift and thus the magnetic field.

2. The magnetometer of claim 1, wherein the solid state electronic spin system comprises a crystal containing a defect.

3. The magnetometer of claim 1, further comprising an optical source configured to generate the optical excitation radiation that causes the electronic spins to align with the magnetic field.

4. The magnetometer of claim 3, wherein the optical source comprises a laser.

5. The magnetometer of claim 2, wherein the crystal comprises a diamond, and wherein the defect comprises an NV (Nitrogen vacancy) center.

6. The magnetometer of claim 4, wherein the optical excitation radiation is laser light having a wavelength of about 530 nanometers.

7. The magnetometer of claim 1, wherein the external control comprises RF radiation, and wherein each electronic spin is configured to precess around an axis of the magnetic field in response to the RF radiation.

8. The magnetometer of claim 7, further comprising an RF source configured to generate the RF radiation that induces the precession of the electronic spins about the magnetic field when applied to the aligned electronic spins.

9. The magnetometer of claim 8, wherein the RF source comprises an RF pulse generator that generates an excitation RF field that can be applied in any desired direction relative to the magnetic field.

10. The magnetometer of claim 5, wherein the sensitivity of the magnetometer for a single NV center is about 200 nT Hz⁻

1/2 when the magnetic field is a DC magnetic field, and about 10 nT Hz<sup>−

1/2</sup> when the magnetic field is an AC magnetic field.

11. The magnetometer of claim 1, wherein the crystal has a diameter of about 10 nm to about 100 nm, and wherein the magnetometer has a corresponding spatial resolution ranging from about 10 nm to about 100 nm.

12. The magnetometer of claim 1, wherein the detector comprises a CCD (charge-coupled device) and one or more associated optical components.

13. The magnetometer of claim 1, wherein the detector comprises one of:

a confocal microscope; and

a super-resolution imaging system configured to implement one or more techniques for imaging below the conventional diffraction limit.

14. The magnetometer of claim 13, wherein the one or more techniques comprise STED (stimulated emission depletion).

15. The magnetometer of claim 7, wherein the detector is configured to employ magnetic field gradients to improve spatial resolution by localizing the spatial region in which the electronic spins are on resonance with the applied RF radiation.

16. The magnetometer of claim 11, further comprising an AFM (atomic force microscope), and wherein the crystal is mounted at the tip of the AFM.

17. The magnetometer of claim 1, wherein the detector comprises a control and data processing system configured to determine the Zeeman shift and the magnetic field from the detected output optical radiation, and wherein the Zeeman frequency shift δ

ω

is proportional to the magnetic field according to a formula given by;

18. The magnetometer of claim 3, further comprising one or more optical components configured to direct the optical excitation radiation from the optical source toward the electronic spin system, and further configured to direct the output optical radiation from the electronic spin system toward the detector.

34. The magnetometer of claim 18, wherein the one or more optical components comprises a dichroic mirror.

19. A magnetometer for sensing a magnetic field, comprising:

a macroscopic sample of a solid that includes a crystal lattice and a relatively high density of electronic spins within the lattice, the electronic spins being substantially free of interactions with the lattice;

wherein the electronic spins are configured to align with the magnetic field when optical excitation radiation is applied to the electronic spins; and

wherein the electronic spins can be further manipulated by an external control so as to induce a precession of the electronic spins about the magnetic field to be sensed, the frequency of the precession being linearly related to the magnetic field by the Zeeman shift of the electronic spin energy levels; and

a detector configured to detect output optical radiation from the sample after the electronic spins in the sample have been subject to the optical excitation radiation and the external control, so as to determine the Zeeman shift and thus the magnetic field.

20. The magnetometer of claim 19, further comprising an optical source configured to generate the optical excitation radiation that causes the electronic spins to align with the magnetic field.

21. The magnetometer of claim 20, wherein the optical source comprises a laser.

22. The magnetometer of claim 21, wherein the optical radiation is laser light having a wavelength of about 530 nanometers.

23. The magnetometer of claim 20, wherein the external perturbation comprises RF radiation, and further comprising an RF source configured to generate the RF radiation that induces the precession of the electronic spins about the magnetic field when applied to the aligned electronic spins.

24. The magnetometer of claim 23, wherein the RF source comprises an RF pulse generator that generates an excitation RF field that can be applied in any desired direction relative to the magnetic field.

25. The magnetometer of claim 19, wherein the detector comprises a CCD (charge-coupled device) array and one or more associated optical components.

26. The magnetometer of claim 19, wherein the detector comprises a system control and data processing system configured to determine the Zeeman shift and the magnetic field from the detected output optical radiation, and wherein the Zeeman frequency shift δ

ω

is proportional to the magnetic field according to a formula given by;

27. The magnetometer of claim 20, further comprising one or more optical components configured to direct the optical excitation radiation from the optical source toward the electronic spin system, and further configured to direct the output optical radiation from the electronic spin system toward the detector.

28. The magnetometer of claim 19, wherein the crystalline solid comprises a diamond, and wherein the electronic spins comprise NV centers in the diamond.

29. The magnetometer of claim 19, wherein the density of the electronic spins is about 10¹⁸ cm⁻

3, and wherein an average distance between the electronic spins is about 10 nm.

30. A method of detecting a magnetic field, comprising:

applying optical excitation radiation to a solid state electronic spin system that contains at least one or more electronic spins within a solid state lattice, thereby aligning the electronic spin or spins with the magnetic field;

applying one or more pulses of RF radiation to the solid state electronic spin system so as to induce a precession of the electronic spins about the magnetic field to be sensed, the frequency of this precession being linearly related to the magnetic field by the Zeeman shift of the electronic spin energy levels; and

detecting output optical radiation from the solid state electronic spin system after the optical excitation radiation and the RF radiation have passed through the electronic spins in the solid state electronic spin system, so as to determine the Zeeman shift and thus the magnetic field from the output radiation.

31. The method of claim 30, wherein the solid state electronic spin system comprises a crystal containing one or more defects.

32. The method of claim 31, wherein the crystal comprises a diamond, and wherein the defects comprise NV centers.

33. The method of claim 30, wherein the act of applying one or more pulses of RF radiation to the solid state electronic spin system comprises applying a sequence of RF pulses to the solid state electronic spin system.